Conduits are often connected together by couplings with fluid under pressure from a source of pressurized fluid, such as a compressor in an air conditioner system, so that even though the compressor may not be in operation, fluid under pressure may still be in the conduits when it is necessary to disconnect them from the source of pressurized fluid. To effect this disconnection of the conduits the coupling should be constructed so that it can be partly disconnected so as to permit venting of fluid pressure from the conduits before the coupling is completely disconnected.
It is highly desirable that the venting of pressure during disconnection of the coupling be positively performed so that even in the case of sticking seals or other parts the pressure will necessarily be released before complete disconnection. It also is preferred that the operation of the coupling, connecting as well as disconnecting, can be carried out without special tools.
Many coupling designs with two stages of disconnection for pressure relief have been proposed. The U.S. Pat. No. 3,718,350 to Klein, shows a coupling with a plug carrying an O-ring seal insertable into a socket. Annular shoulders in the socket cooperate with a split retaining ring in the plug to hold the coupling in a pressure relief state after the retaining ring has been released from its fully engaged position. Special tools are required to release the retaining ring.
Another Klein patent, U.S. Pat. No. 3,574,359, has a double O-ring seal carried by a plug and inserted into a socket. Two sets of detentes held in place by a threaded sleeve make a two stage disconnection possible but there is no positive release of pressure so that the detentes could all be removed prior to removing the plug from the socket. The U.S. Pat. No. 3,847,421 to Eschbaugh achieves similar results. A plug carrying an O-ring is inserted into a socket and held there by a threaded nut engaging the socket and bearing against a bead on the plug via a sheet metal collar. The nut has sufficient threaded extent to be partially backed off to allow pressure release but there is no mechanism to assure the seal will be broken at that time. The nut may be completely removed while the seal is intact and the pressure still present.
U.S. Pat. No. 3,826,523 to Eschbaugh shows a socket with an interior shoulder, a plug with a bead for holding an O-ring into the socket and a collet with long fingers abutting the shoulder to maintain the assembly and a short finger to engage the shoulder when the long fingers are released upon disassembly, thus holding the plug in a pressure relief state.
U.S. Pat. No. 3,584,902 to Vyse uses a double O-ring seal in a plug and socket coupling and has two spaced retaining clips which must be removed one at a time for disassembly. The second clip can be removed only when the seal has been partly broken for slow pressure release.
Thus many approaches to the pressure relief requirement have been proposed. Some merely provide the opportunity for the operator to release the pressure prior to complete decoupling, there being no positive seal breaking at the second stage of disconnection. Some require elaborate mechanisms with many parts and even clips or small detentes which make reassembly a time consuming operation.